Extreme treehouses

Local artists and architects have re-imagined treehouses for a whimsical summer display at the Minnesota Landscape Arboretum. One structure sits among the oldest tree on the grounds, while others take on variations of birdhouses, an oculus or underground fortress. Fans can vote for their favorite and votes will be tallied in the fall to declare the winner. Guests can create their own mini tree structure on Saturday with provided supplies. Guests can also bring accessories to enhance their craft. (8 a.m.-8 p.m. Sat., activity hours 10 a.m.-noon. $15. 3675 Arboretum Dr., Chaska. 952-443-1400. arboretum.umn.edu.)